My picks:
-Bite of the Werebeast line - +16 Str and free feats in addition to the natural strength of wildshaped druids / animal companions? Uhuh.
-Ray of Stupidity - it's not just the Int-3 foes who have to worry about this. Ability damage stacks. Think about Split Ray Empowered Rays of Stupidity. Average 10 Int damage will take down a
lot of creatures - and the ones with higher Int often NEED that Int, an NPC wizard who's just lost 10 Int is probably quite sad.
-(Greater) Consumptive Field - I don't understand why anyone thought a spell that let you get +unlimited Str for killing sufficient bunnies was a good idea... admittedly it's a lot worse Persisted, but even the rounds/level version is pretty exploitable.
-Wraithstrike - enough has been said.
-Mass Resist Energy - a few levels higher and it would probably be fine.
-Imbue Familiar With Spell Ability - maybe. It's dangerous in that it effectively grants extra actions to the PC. It's probably less worrisome if you allow a lot of the good alternate class features that trade in your familiar.
I don't have a major problem with the Orb spells, although I also would have no problem with a houserule moving them to Evocation. They're mostly just mediocre single-target damage with a minor rider effect - backup options for the (hopefully rare) case where your caster doesn't have anything better to do. (To justify "mediocre damage" - I'm comparing to "the damage I would get by using that action and spell-slot to D-Door the big tank fighter next to her target for a full attack".)
I don't think Delay Death is broken so long as you actually enforce immediate action rules - can't be used when flat-footed, only once per round, and they eat your swift action for the next round. I also take the interpretation that you have to cast it before the attack is resolved - Close Wounds is an explicit exception to the usual immediate-action rules. Having played a cleric with it for several levels, I'd also note that there are a lot of other really good L4 cleric spells to compete with it.
Now, if you use the Destiny domain from Races of Destiny, but the version of Delay Death from SpC, then it's a L3 domain spell - and therefore can be chained with a lesser metamagic rod of chaining (which is pretty cheap in the MIC). THAT can be broken, because the party chips in for the cleric to buy L3 pearls of power, and then every fight begins with "I cast chained Delay Death on the entire party as soon as I'm not flatfooted". That's a combo issue, though.
Brambles... meh. It's rounds/level and you have to be wielding a wooden weapon, possibly a wooden bludgeoning weapon depending on how you interpret "striking surfaces".
Rhino's Rush can be used to great effect, but if you're going to ban that one, be fair and ban Lion's Charge as well. Don't give the druids all the charging fun at the expense of the poor paladins
In the somewhat related category of "spells that make your players hate you", I would list Ray Deflection and Ironguard, with an honorable mention to Scintillating Scales (I've fought a dragon with this, and we'd already used up all our dispels - not pretty). Ray Deflection and Ironguard do a pretty good job of shutting down whole classes of attacks that people may have specialized in. Fleshshiver is also a lot scarier on NPCs than on PCs - NPCs tend to have access to more ways to boost CL (especially if the CL is based on HD for some reason).
Re belt of battle: my sorcerer loved hers. That said, she took it off a pouncemonster barbarian ("I shocktrooper-charge-pounce, full power attacking with no penalty to hit! Then I use my belt of battle and full attack you again - still full power attacking with no penalty to hit!"), so I think she earned it

Being able to effectively quicken a top-level spell can be extremely useful.
EDIT: Re Celerity - part of the problem is combos with the Arcane Fusion line from Complete Mage. Another part is the ability to get daze immunity (e.g. from Favor of the Martyr - although given that makes you immune to "effects that would cause you to be dazed", you could argue that it makes you immune to the WHOLE effect of Celerity, including the good bits). But even used just as written... being able to take standard actions as immediates is powerful. After my first game with Celerity on my sorcerer I thought of a bunch of ways I could have used it (but didn't think of at the time, due to being sick and sleep-deprived) - for example, if I'd used Celerity to cast Spiritwall or Wall of Force when the Balor exploded, we would've needed a lot less healing. Another application is being able to interrupt enemy spellcasting without having to ready an action (cast Celerity when they start casting, toss a damage spell or a Silence in their direction, or something that blocks their line of effect). It's also very good for first-round novas - I've been on the receiving end of swift-action spell + Chained Greater Dispel (to shut down visible magic items and dispel all buffs below CL 26, in that case) + Celerity + Sudden Extended Timestop, and that was painful - there were over 100 levels of spells on the battlefield by the time anyone in my L14 party got to act.